Point-to-point wired Dynaco ST-70

[vinylkid58]

I would like to know why the 12AU7 was selected for use with some other mods. I personally think it is a poor choice; the 6CG7/6FQ7 is more linear and better sounding, IMHO.

I agree. If you're going to all the trouble of P-P, why not use a decent tube/tubes in the process?

jeff

 

[ricohman]

Myself is more used to listen to my amp then observing it's outer beauty.
And the suggestion to have the board connected via connectors AND
be mounted from above was a purley functional suggestion, done to
make it easier to remove/replace the board. All in interest of improving
sound and or function.

If main goal is to look nice, then by all means don't listen to my humble suggestion.

As we do have different goals we really should not have an argument here,
please do not see this post as critisism.

Regards

I don't.
I do prefer function and aesthetics as one.
The P51 Mustang is a good example. So is a Ducati 916.
My BMW R1150GSA, not so much.

NOS Valves VRD with the cherry base is very nice to look at. And I can see why the OP's ST70 look like it does.

 

[EliFisk]

I don't.
I do prefer function and aesthetics as one.

NOS Valves VRD with the cherry base is very nice to look at.

Funny - I have a pair of VRDs with cherry base and they are an excellent example of function and aesthetics as one.

 

[GordonW]

I would like to know why the 12AU7 was selected for use with some other mods. I personally think it is a poor choice; the 6CG7/6FQ7 is more linear and better sounding, IMHO. Filament current draw is an issue with this tube because the Dyna doesn't give enough transformer reserve.

Heater/filament draw should not have been an issue; the ST70 power transformer is rated to run not only itself, but TWO Dynaco PAM-1 preamps through the octal takeoff sockets. Each PAM-1 has two 12AX7s in it.

Here's how the heater/filament current totals would compare (ignoring the EL34s and rectifier, as they would be common to both):

Stock- two 7199s (.45 amp each) and (with PAM-1s connected) four 12AX7s (.3a each) = .9 amp + 1.2amp = 2.1 amp.

Modified- one 12AX7 (.3 amp) plus two 6CG7 (.6 amp each = .3 amp + 1.2 amp = 1.5 amp.

It'd still be less than the specified max load on the transformer, in normal conditions...

Regards,
Gordon.

 

[EliFisk]

The best ST70 mod to my ears is the Welbourne Labs mu-follower circuit, but their customer service is unreliable and often horrendous.

I would like to know why the 12AU7 was selected for use with some other mods. I personally think it is a poor choice; the 6CG7/6FQ7 is more linear and better sounding, IMHO. Filament current draw is an issue with this tube because the Dyna doesn't give enough transformer reserve.

The VRD circuit uses a 12AU7 for each channel, which would be why this tube was used. It's difficult to fault the sound of the VRD circuit ;-)